Wood comprises mainly of cellulose, hemicelluloses and lignin. Hitherto lignin has been underutilized, main reason for that being the little information that has been known about its native structure. The extraction of lignin for analytical purposes is not easily accomplished without harsh conditions or mechanical pre-treatments to reduce the particle size and expose the biopolymers through an increased surface area made available. Ball milling is such a pre-treatment. However, the effect it has on the structure of wood biopolymers is still poorly understood. This study focuses on the effect of ball milling as a function of time and in different milling atmospheres. A new protocol is developed, enabling the extraction of different lignin populations in spruce under mild conditions. These populations were then thoroughly studied by advanced techniques (1D and 2D NMR, SEC and XRD). Overall, the role of synergies between supramolecular and molecular events in lignin molecular heterogeneity is reported. Finally, a model of the fiber wall based on the findings of this study is also proposed, and a mechanism of its disintegration during ball milling discussed.

Lignin population studies in ball milled spruce wood

ACS Spring Meeting 2021

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